1. Field of the Invention
The present invention relates to bicycle helmets, in particular to sizing and stabilizing a mountain bike helmet on a rider's head.
2. Discussion of the Prior Art
Lightweight helmets for head protection during bicycle riding falls and accidents have continuously evolved and undergone numerous improvements in recent years. One particular area of refinement has been in the fitting and stabilizing of helmets on the bicycle rider's head. An example of a prior art bicycle helmet and a means for securing it from excessive movement is disclosed in U.S. Pat. No. 4,903,350.
In order to fit a variety of head shapes and sizes, a particular brand of helmet often will be available in several sizes. Each size typically can be customized to a particular wearer's head by inserting or removing cushions and pads around the interior of the helmet cavity to obtain a snug fit.
Chin straps are employed to keep the helmet on. These straps reduce the vertical movement of the helmet relative to the wearer's head, but provide little resistance to the forward and back rocking motion of the helmet. Many helmet models now employ chin straps having a "Y" configuration on each side. A loop is attached to the front and rear of each side of the helmet, and these two loops are connected by a strap beneath the wearer's chin. An example of this type of prior art helmet and strap arrangement is also disclosed by U.S. Pat. No. 4,903,350. While this type of chin strap reduces the amount of helmet movement, it does not eliminate it.
The sport of mountain bike riding has grown increasingly popular in recent years. This activity involves riding specially designed bicycles with heavy duty frames and components on unpaved roads, trails and rough terrain. Experienced mountain bike riders can travel over steep drops, uneven terrain, boulders, stumps, logs, creek beds, and such while on their mountain bikes. Conventional bicycle helmets are typically used for protection from falls. The bouncing, bumping and jarring associated with mountain bike riding greatly exacerbates the problem of excessive helmet movement on the rider's head. Bike riders traveling on dirt roads or even city streets will often experience these problems. A tightly fitted helmet with a taut chin strap may reduce the amount of movement of the helmet on the wearer's head, but usually provides more of a discomfort than a solution to the problem.
Prior art bicycle helmets have not utilized the undercut portion beneath the occipital region of the wearer's head to stabilize the helmet. There are two apparent reasons for this. The first is that the process used to mold a one piece main shell of the helmet can not tolerate a negative draft angle without prohibitively expensive multi-part molds to allow removal of the helmet after molding. The second reason concerns the difficulty or impossibility of the wearer fitting the helmet over his or her head if the helmet contains a substantial inward curve to match the undercut portion of the back of the head.